A campaign to eradicate cats from New Zealand in a bid to preserve native birdlife has left pet lovers howling with outrage.

The controversial call to rid the country of cats is being led by Gareth Morgan, a prominent businessman, who tells owners on his newly created Cats to Go website: "The fact is that your furry friend is actually the friendly neighbourhood serial killer."

Under a picture of a kitten with red devil's horns, the website asserts "cats are the only true sadists of the animal world" and that they "torture their victims slowly and without mercy".

It goes on: "Every year, hundreds of millions of birds are murdered by cats.

"Some cats will kill over a thousand birds each year."

Although the campaign stops short of calling for cats to be euthanised, it points out that that is an option.

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It also calls on cat owners to keep their pet inside 24 hours a day and, when the time comes, "ensure this is the last cat you ever own".

Cats should also be neutered and have a bell hung around their necks to warn birds they are nearby, it says.

The website asks for signatures on a petition calling for cats to be registered and micro-chipped like dogs.

"Imagine a New Zealand teeming with native wildlife, penguins on the beach, kiwis roaming about in your garden," Mr Morgan says.

"Imagine hearing birdsong in our cities."

New Zealand is renowned for its unique birdlife, most of which flourished for thousands of years without predators.

So benign was the natural environment that species such as the kiwi, the national symbol, became flightless.

But Mr Morgan's campaign was bound to spark an angry backlash in a country that owns more cats per capita than any other, with nearly half of all households having at least one.

Cat lovers were quick to take to the internet and talkback radio to air their protests.

Some have even set up anti-Gareth Morgan web pages.

More than 70 per cent of visitors to the Cats to Go website expressed disapproval of the proposals, while on news websites, comments such as "Mess with my cat and I'll mess with you" summed up the mood.

Bob Kerridge, executive director of the Society for the Prevention of Cruelty to Animals, rounded on Mr Morgan, saying: "Butt out of our lives.

"Don't deprive us of the beautiful relationship that a cat can provide, individually and as a family.

"People consider cats to be a member of the family.

"So he's trying to, quite frankly, take away the civil liberties we all have, to choose who we want in our home."

Other protesters claim cats may actually help protect bird numbers by preying on the rodents that eat their eggs.